U.S. patent number 6,985,212 [Application Number 10/440,918] was granted by the patent office on 2006-01-10 for laser perimeter awareness system.
This patent grant is currently assigned to Rosemount Aerospace Inc.. Invention is credited to James R. Jamieson, Mark D. Ray.
United States Patent |
6,985,212 |
Jamieson , et al. |
January 10, 2006 |
**Please see images for:
( Certificate of Correction ) ** |
Laser perimeter awareness system
Abstract
A method of laser scanning a perimeter zone of a target site for
the detection of potential threats comprises: scanning a pulsed
laser beam across the perimeter zone; receiving echoes from the
pulsed laser beam during the perimeter zone scan; deriving range
data corresponding to the received echoes; determining position
data of the received echoes in the perimeter zone; forming a scene
image of a scan of the perimeter zone based on the range and
position data of the received echoes thereof; repeating the steps
of scanning, receiving, deriving, determining and forming for a
plurality of perimeter zone scans to form scene images of each scan
of the plurality; and comparing scene images of the plurality to
detect a potential threat in the perimeter zone. In addition, a
method of authenticating a potential threat detected in a perimeter
zone of a target site comprises: detecting the potential threat and
upon detection, interrogating the potential threat for a response
by a wireless transmission; declaring the potential threat
unauthorized if no response is transmitted wirelessly within a
predetermined time interval from the interrogation; receiving the
response, if transmitted, and determining if the response comprises
a proper access code; and declaring the potential threat
unauthorized if the received response is determined not to comprise
the proper access code.
Inventors: |
Jamieson; James R. (Savage,
MN), Ray; Mark D. (Burnsville, MN) |
Assignee: |
Rosemount Aerospace Inc.
(Burnsville, MN)
|
Family
ID: |
33449907 |
Appl.
No.: |
10/440,918 |
Filed: |
May 19, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20040233414 A1 |
Nov 25, 2004 |
|
Current U.S.
Class: |
356/5.01;
356/139.03 |
Current CPC
Class: |
G01S
17/74 (20130101); G01S 17/86 (20200101); G01S
17/42 (20130101); G01S 17/89 (20130101); G01S
17/66 (20130101); G01S 13/86 (20130101); G01S
13/78 (20130101); G01S 17/58 (20130101); G01S
7/4802 (20130101); G01S 7/4811 (20130101); G01S
7/4818 (20130101) |
Current International
Class: |
G01C
3/08 (20060101); G01B 11/26 (20060101); G01C
1/00 (20060101) |
Field of
Search: |
;356/5.01-5.08,139.04-139.08,147,139.03 ;348/153-155,143
;340/961-963,541,600 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
PCT International Search Report. cited by other.
|
Primary Examiner: Gregory; Bernarr E.
Assistant Examiner: Andrea; Brain
Attorney, Agent or Firm: Calfee, Halter & Griswold LLP
Rashid, Esq.; James M.
Parent Case Text
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
U.S. patent application Ser. No. 10/109,372, filed Mar. 28, 2002,
and entitled "Distributed Laser Obstacle Awareness System";
U.S. patent application Ser. No. 10/251,422, filed Sep. 20, 2002,
and entitled "Railway Obstacle Detection System and Method";
U.S. patent application Ser. No. 10/347,908, filed Jan. 21, 2003,
and entitled "System For Profiling Objects On Terrain Forward and
Below An Aircraft Utilizing A Cross-Track Laser Altimeter";
All of the above referenced patent applications are assigned to the
same assignee as the instant application.
Claims
We claim:
1. Method of laser scanning a perimeter zone of a target site for
the detection of an object, said method comprising the steps of:
pulsing a laser beam at a predetermined pulse repetition rate;
oscillating said pulsed laser beam through a predetermined angle in
a first direction; scanning said oscillating pulsed laser beam in a
second direction across said perimeter zone; receiving echoes from
said pulsed laser beam during said perimeter zone scan; deriving
range data corresponding to said received echoes; determining
two-dimensional position data of said received echoes in said
perimeter zone; forming a three-dimensional scene image of a scan
of said perimeter zone based on said range and two-dimensional
position data of said received echoes thereof; repeating the steps
of scanning, deriving, determining and forming for a plurality of
perimeter zone scans to form three-dimensional scene images of each
scan of said plurality; and comparing the three-dimensional scene
images of said plurality to detect the object in said perimeter
zone.
2. The method of claim 1 including the steps of: oscillating the
pulsed laser beam back and forth through a predetermined elevation
angle; and scanning said oscillating pulsed laser beam across an
azimuth angle to form a sinusoidal scan pattern across the
perimeter zone.
3. The method of claim 1 wherein the step of deriving includes
deriving the range data corresponding to received echoes based on
laser pulse-to-echo time of flight derivations.
4. The method of claim 1 wherein the step of comparing includes the
steps of: assigning at least one scene image of said plurality as a
reference scene; detecting at least one moving object in the
perimeter zone by a comparison of other scene images of said
plurality to said reference scene image; and assigning a threat
priority level to each detected moving object.
5. The method of claim 4 wherein the step of detecting includes the
step of: detecting the at least one moving object in the perimeter
zone by detecting a change in at least one of the range and
two-dimensional position thereof by the comparison of other scene
images of said plurality to said reference scene image.
6. The method of claim 4 wherein the step of assigning includes the
steps of: tracking the at least one moving object in range and
two-dimensional position with respect to the target site among the
scene images of the plurality; and assigning a threat priority
level to each detected moving object based on said track
thereof.
7. The method of claim 4 wherein the step of assigning includes the
steps of: tracking the at least one moving object in range and
two-dimensional position with respect to the target site among the
scene images of the plurality; assigning a threat priority level to
each detected moving object based on a constant bearing, decreasing
range (CBDR) algorithm; and queuing each detected moving object in
a queue based on said assigned threat priority level thereof.
8. The method of claim 4 including the step of displaying a
three-dimensional image representation of the at least one moving
object on a display screen.
9. The method of claim 4 including the step of positioning a
spotlight on one of the at least one moving object based on the
threat priority level thereof.
10. The method of claim 4 including the step of positioning a
camera to view one of the at least one moving object based on the
threat priority thereof.
11. The method of claim 10 including the steps of displaying an
image of the camera view on a display screen; and overlaying an
image representation of the at least one moving object on top of
the camera view in the display screen.
12. The method of claim 4 including the steps of: determining the
shape of the detected at least one moving object; comparing said
shape of the at least one moving object with known shapes; and
determining if said at least one moving object is friendly based on
results of said shape comparing step.
13. A system for laser scanning a perimeter zone of a target site
for the detection of an object, said system comprising: a laser
source for generating a pulsed laser beam; an oscillating unit for
oscillating said pulsed laser beam through a predetermined angle in
a first direction; a scanning unit for scanning said oscillating
pulsed laser beam in a second direction across said perimeter zone
and for receiving echoes from said pulsed laser beam during said
perimeter zone scan, said scanning unit operative to generate
electrical position signals corresponding to two-dimensional
positions of said received echoes in the perimeter scan; a light
detector for converting said received echoes into electrical echo
signals representative thereof; and a signal processor for
receiving the electrical echo signals and corresponding position
signals and for forming three-dimensional scene image data
corresponding to a plurality of perimeter zone scans based on said
electrical echo signals and corresponding two-dimensional position
signals; said signal processor operative to compare the
three-dimensional scene image data of said plurality of perimeter
zone scans to detect the object in said perimeter zone.
14. The system of claim 13 including a memory for storing the
formed scene image data.
15. The system of claim 13 including fiber optic cabling for
coupling the pulsed laser beams from laser source to the scanning
unit.
16. The system of claim 13 including fiber optic cabling for
coupling the received echoes from the scanning unit to the light
detector.
17. The system of claim 13 wherein the oscillating unit is part of
scanning unit and includes an optical element driven to oscillate
the pulsed laser beam back and forth through a predetermined
elevation angle, said optical element also driven to rotate the
oscillating pulsed laser beam through a predetermined azimuth angle
to cover the perimeter zone.
18. The system of claim 13 wherein the signal processor comprises a
programmed digital processor operative to assign at least one scene
image of the plurality as a reference scene, to detect at least one
moving object in the perimeter zone by a comparison of other scene
images of the plurality to said reference scene image; and to
assign a threat priority level to each detected moving object.
19. The system of claim 18 includes a spotlight; and wherein the
programmed digital processor is operative to position said
spotlight on one of the at least one moving object based on the
threat priority level thereof.
20. The system of claim 18 includes a camera; and wherein the
programmed digital processor is operative to position said camera
to view the at least one moving object based on the threat priority
level thereof.
21. The system of claim 20 including a display unit coupled to the
camera for displaying an image of the camera view on a screen
thereof; and an overlay control unit coupled between the processor
and the display unit for overlaying images and text onto the camera
view image display; and wherein the processor is operative to
provide three-dimensional image representations of the at least one
moving object to the overlay control unit for being overlaid onto
the camera view image display.
22. The system of claim 18 including a display unit; and wherein
the processor is operative to display a three-dimensional image
representation of the at least one moving object on a screen of the
display unit.
23. The system of claim 17 including: a plurality of scanning
units, each scanning unit of said plurality for scanning a pulsed
laser beam across a different perimeter zone surrounding the target
site and for receiving echoes from the pulsed laser beam during
said corresponding perimeter zone scan, each scanning unit
operative to generate electrical position signals corresponding to
two-dimensional positions of said received echoes in the
corresponding perimeter scan; at least one light detector for
converting said received echoes from the plurality of scanning
units into electrical echo signals representative thereof; a signal
processor for receiving the electrical echo signals and
corresponding two-dimensional position signals and for forming
three-dimensional scene image data corresponding to a plurality of
scans of each different perimeter zone based on said electrical
echo signals and corresponding two-dimensional position signals;
said signal processor operative to compare the scene image data of
said plurality of scans of each different perimeter zone to detect
the object in at least one of the different perimeter zones.
24. Method of laser scanning a perimeter zone of water from a
search vehicle for the detection of an object in the water, said
method comprising the steps of: oscillating a pulsed laser beam
through a predetermined angle in a first direction; scanning said
oscillating pulsed laser beam in a second direction across a
surface of said perimeter zone of water; receiving echoes from said
pulsed laser beam during said perimeter zone scan; deriving range
data corresponding to said received echoes; determining
two-dimensional position data of said received echoes in said
perimeter zone; forming three-dimensional scene image data of a
scan of said perimeter zone based on said range and two-dimensional
position data of said received echoes thereof; and detecting the
object in said perimeter zone of water from said scene image
data.
25. The method of claim 24 wherein the pulsed laser beam is scanned
downward across the water surface from an aircraft search
vehicle.
26. The method of claim 24 wherein the pulsed laser beam is scanned
downward across the water surface from a marine search vehicle.
27. The method of claim 24 including the step of displaying a
three-dimensional image representation of the detected object on a
display screen.
28. The method of claim 24 including the step of detecting an
individual in the perimeter zone of water from the scene image
data.
29. The method of claim 24 including the steps of: repeating the
steps of scanning, receiving, deriving, determining and forming for
a plurality of perimeter zone scans to form three-dimensional scene
image data of each scan of said plurality; and comparing the
three-dimensional scene image data of said plurality of scans to
detect the object in said perimeter zone of water.
30. A system for laser scanning a perimeter zone of water from a
search vehicle for the detection of an object in the water, said
system comprising: a laser source for generating a pulsed laser
beam; an oscillating unit for oscillating said pulsed laser beam
through a predetermined angle in a first direction; a scanning unit
for scanning said oscillating pulsed laser beam in a second
direction across a surface of said perimeter zone of water and for
receiving echoes from said pulsed laser beam during said perimeter
zone scan, said scanning unit operative to generate electrical
position signals corresponding to two-dimensional positions of said
received echoes in the perimeter scan; a light detector for
converting said received echoes into electrical echo signals
representative thereof; a signal processor for receiving the
electrical echo signals and corresponding position signals and for
forming three-dimensional scene image data corresponding to a
perimeter zone scan based on said electrical echo signals and
corresponding two-dimensional position signals; and said signal
processor operative to process the three-dimensional scene image
data to detect the object in the perimeter zone of water.
31. The system of claim 30 including a spotlight disposed on the
search vehicle; and wherein the signal processor is operative to
position the spotlight to highlight the detected object in the
water.
32. The system of claim 30 including a camera disposed on the
search vehicle; and wherein the signal processor is operative to
position said camera to view the detected object in the water.
33. The system of claim 30 including a display unit; and wherein
the processor is operative to display a three-dimensional image
representation of the detected object on a screen of the display
unit.
34. The system of claim 30 wherein the oscillating unit is part of
the scanning unit and includes an optical element driven to
oscillate the pulsed laser beam back and forth through the
predetermined angle, said optical element also driven to rotate the
oscillating pulsed laser beam through a second predetermined angle
in the second direction to cover the perimeter zone; and including:
a plurality of scanning units, each scanning unit of said plurality
for scanning a pulsed laser beam across a different perimeter zone
of water surrounding the search vehicle and for receiving echoes
from the pulsed laser beam during said corresponding perimeter zone
scan, each scanning unit operative to generate electrical position
signals corresponding to two-dimensional positions of said received
echoes in the corresponding perimeter scan; at least one light
detector for converting said received echoes from the plurality of
scanning units into electrical echo signals representative thereof;
a signal processor for receiving the electrical echo signals and
corresponding two-dimensional position signals and for forming
three-dimensional scene image data corresponding to a scan of each
different perimeter zone based on said electrical echo signals and
corresponding two-dimensional position signals; said signal
processor operative to process the three-dimensional scene image
data of each different perimeter zone to detect the object in at
least one of the different perimeter zones.
35. The system of claim 30 wherein the search vehicle is an
aircraft; and wherein the scanning unit is disposed on the aircraft
to scan the pulsed laser beam downward across the water surface
from the aircraft search vehicle.
36. The system of claim 30 wherein the search vehicle is a marine
vessel; and wherein the scanning unit is disposed on the marine
vessel to scan the pulsed laser beam downward across the water
surface from the marine vessel.
37. The system of claim 30 wherein the signal processor is
operative to process the scene image data to detect an individual
in the perimeter zone of water.
38. The system of claim 30 wherein the processor is operative to
form three-dimensional scene image data corresponding to a
plurality of perimeter zone scans based on said electrical echo
signals and corresponding two-dimensional position signals, and to
compare the three-dimensional scene image data of said plurality of
perimeter zone scans to detect the object in the perimeter zone of
water.
Description
BACKGROUND OF THE INVENTION
The present invention is related to perimeter security and search
and rescue systems, in general, and more particularly, to a system
for and method of laser scanning a perimeter zone around a target
site to render an awareness of potential threats to such target
site, and a system for and method of laser scanning a perimeter
zone of water around a search vehicle to detect an object floating
in the water.
With the increase of worldwide asymmetric terrorist activities,
close in and long range proximity identification of potential
threats to a target is of paramount interest. Today such threats
may come in many forms such as suicide bombers, car bombs, shoulder
launched missiles, rocket propelled grenades, and saboteurs among
others. Terrorist targets such as heavily populated civilian and
governmental facilities, military bases, aircraft, marine vessels
and commercial businesses, for example, continue to expand
worldwide. Likewise, these threats have also escalated in severity
to now include real scenarios of chemical, biological, and nuclear
attacks. As such, the role of intelligence, surveillance,
reconnaissance, and countermeasure action has and will continue to
be critical in preventing attacks on such targets.
In response to these emerging threats, it is of the ut-most
importance to proactively monitor the surrounding land and
waterside perimeter of threat vulnerable targets. Specifically,
potential target sites such as ports and harbors, vast areas of
land at airports and nuclear sites, military installations, high
visibility sporting events, marine vessels, aircraft and others
have come to the forefront requiring the detection of object motion
and presence. Early identification and warning of objects within a
perimeter of a target is critical in assessing potential threats
and taking appropriate counter-terrorism/military measures. As a
result of our historically open society, terrorists have numerous
opportunities to strike our society at vulnerable targets which
heretofore may have only been passively monitored with a security
camera, if at all.
Current perimeter security systems and processes have been
demonstrated to be insufficient for these emerging threats. For
example, video cameras, night vision systems, radar, and
conventional security patrols have proven ineffective at preventing
recent terrorist attacks. Recent events such as the bombing of the
USS Cole, a French oil tanker in Yemen, airport security breaches,
car and suicide bombings, and the launching of rocket propelled
grenades might have been avoided with an early warning system
capable of detecting and tracking motion of objects on the ground
or water. In each case, assailants penetrated traditional security
layers of manned surveillance, video camera, or no security at all
to launch an attack. Early identification and geolocation of
potential ground and marine threats may be critical in thwarting
attempts and securing and sustaining economic, commercial and
military operations worldwide.
In addition, use of conventional radar systems for threat
monitoring may result in confusion due to multi-path returns over
water and will suffer from radar "clutter" at close in ranges
(blind radar zones). These blind zones, depending upon the radar
power, may be on the order of hundreds of meters to kilometers, for
example. Additionally, changes in sea states can degrade the
detection performance of the radar system even further. Algorithms
have been developed in an attempt to suppress the noise generated
due to multiple scattering paths from interaction with swells and
short period surface wave action, but generally are targeted for
detection of large objects, such as ships, for example, over many
kilometers. Further, radar systems also suffer from broad main beam
lobes, on the order of 1-10 degrees. To generate this level of
directivity, side lobes can also be generated creating multi-path
propagation, further reducing the fine detail detection of
conventional radar systems.
Also, as in the case of a search and rescue of a survivor at sea,
like a downed pilot, for example, a person's body floating in water
may be detected by a conventional passive infrared system relying
on the thermal difference between the body and the water. As the
body temperature can be different than that of the water, the body
of a terrorist may be detected by passive infrared sensors.
However, the body temperature of a terrorist may be disguised. Once
the body temperature of the terrorist approaches that of the
surrounding water, the ability to detect the body with passive
infrared sensors quickly diminishes, i.e. the thermal gradients
necessary for an infrared body signature are lost. Thus, under
these circumstances, conventional passive infrared imaging systems
may miss detecting the terrorist's body in the water.
Likewise, in searching for persons in the water as in the case of a
search and rescue mission, while living, sufficient thermal
gradients may exist to enable thermal detection of the person.
However, once deceased, the body temperature approaches that of the
water. In this case, use of thermal imaging for recovery is
voided.
The present invention overcomes the aforementioned drawbacks of the
current perimeter security and search and rescue systems and
provides a laser perimeter awareness system (LPAS) which utilizes a
laser obstacle awareness system for monitoring a perimeter around a
vulnerable target for rendering an awareness of potential threats
to such target or for monitoring a perimeter of water around a
search vehicle for detecting an object floating in the water.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a method of
laser scanning a perimeter zone of a target site for the detection
of potential threats comprises the steps of: scanning a pulsed
laser beam across the perimeter zone; receiving echoes from the
pulsed laser beam during the perimeter zone scan; deriving range
data corresponding to the received echoes; determining position
data of the received echoes in the perimeter zone; forming a scene
image of a scan of the perimeter zone based on the range and
position data of the received echoes thereof; repeating the steps
of scanning, receiving, deriving, determining and forming for a
plurality of perimeter zone scans to form scene images of each scan
of the plurality; and comparing scene images of the plurality to
detect a potential threat in the perimeter zone.
In accordance with another aspect of the present invention, a
system for laser scanning a perimeter zone of a target site for the
detection of potential threats comprises: a laser source for
generating a pulsed laser beam; a scanning unit for scanning the
pulsed laser beam across the perimeter zone and for receiving
echoes from the pulsed laser beam during the perimeter zone scan,
the scanning unit operative to generate electrical position signals
corresponding to positions of the received echoes in the perimeter
scan; a light detector for converting the received echoes into
electrical echo signals representative thereof, a signal processor
for receiving the electrical echo signals and corresponding
position signals and for forming scene image data corresponding to
a plurality of perimeter zone scans based on the electrical echo
signals and corresponding position signals; the signal processor
operative to compare the scene image data of the plurality of
perimeter zone scans to detect a potential threat in the perimeter
zone.
In accordance with yet another aspect of the present invention, a
method of authenticating a potential threat detected in a perimeter
zone of a target site comprises the steps of: detecting the
potential threat in the perimeter zone of the target site; upon
detection, interrogating the potential threat for a response by a
wireless transmission; declaring the potential threat unauthorized
if no response is transmitted wirelessly within a predetermined
time interval from the interrogation; receiving the response, if
transmitted, and determining if the response comprises a proper
access code; and declaring the potential threat unauthorized if the
received response is determined not to comprise the proper access
code.
In accordance with yet another aspect of the present invention, a
system for authenticating a potential threat detected in a
perimeter zone of a target site comprises: a personal communicator
for each person that has access to the perimeter zone, each
communicator operative to transmit wirelessly an authorized access
code in response to a reception of a wirelessly transmitted
interrogation signal; a scanning laser object awareness system
(LOAS) for detecting the potential threat in the perimeter zone of
the target site and for generating a threat detection signal
indicative of the detection; a wireless transmitter/receiver unit;
an authenticator unit coupled to the scanning LOAS and the wireless
transmitter/receiver unit, and responsive to the threat detection
signal to control the wireless transmitter/receiver unit to
transmit the interrogation signal to the potential threat; the
wireless transmitter/receiver unit operative to receive the
response, if transmitted from a personal communicator within a
predetermined area of the detected potential threat; the
authenticator unit operative to declare the potential threat
unauthorized if no response is received within a predetermined time
interval from the interrogation; the authenticator unit further
operative to declare the potential threat unauthorized if the
received response is determined not to comprise an authorized
access code.
In accordance with yet another aspect of the present invention, a
method of, laser scanning a perimeter zone of water from a search
vehicle for the detection of an object in the water comprises the
steps of: scanning a pulsed laser beam across a surface of the
perimeter zone of water; receiving echoes from the pulsed laser
beam during the perimeter zone scan; deriving range data
corresponding to the received echoes; determining position data of
the received echoes in the perimeter zone; forming scene image data
of a scan of the perimeter zone based on the range and position
data of the received echoes thereof; and detecting the object in
the perimeter zone of water from the scene image data.
In accordance with yet another aspect of the present invention, a
system for laser scanning a perimeter zone of water from a search
vehicle for the detection of an object in the water comprises: a
laser source for generating a pulsed laser beam; a scanning unit
for scanning the pulsed laser beam across a surface of the
perimeter zone of water and for receiving echoes from the pulsed
laser beam during the perimeter zone scan, the scanning unit
operative to generate electrical position signals corresponding to
positions of the received echoes in the perimeter scan; a light
detector for converting the received echoes into electrical echo
signals representative thereof; a signal processor for receiving
the electrical echo signals and corresponding position signals and
for forming scene image data corresponding to a perimeter zone scan
based on the electrical echo signals and corresponding position
signals; and the signal processor operative to process the scene
image data to detect the object in the perimeter zone of water.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of an exemplary laser perimeter awareness
system suitable for embodying the broad principles of the present
invention.
FIG. 2 is a cross-section view of one of the laser perimeter zone
scans of the embodiment of FIG. 1.
FIG. 3 is an illustration of a scan head suitable for use in the
embodiment of FIGS. 1 and 2.
FIG. 4 is sketch exemplifying optical elements suitable for use in
the scan head embodiment of FIG. 3.
FIG. 5 is a block diagram schematic of a laser perimeter awareness
system suitable for use in the embodiment of FIGS. 1 and 2.
FIGS. 6A and 6B depict a program flowchart suitable for use in
programming a digital signal processor of the embodiment of FIG.
5.
FIG. 7 is a composite illustration of stored historical data of
moving objects over a plurality of scene images.
FIG. 8 is an exemplary queue table for prioritizing detected
potential threats.
FIG. 9 is an illustration of an automated authentication system
suitable for embodying another aspect of the present invention.
FIG. 10 is a block diagram schematic of an exemplary authentication
system suitable for use in the embodiment of FIG. 9.
FIG. 11 is an illustration of a search and rescue application of
the laser perimeter awareness system from an aircraft search
vehicle over water in accordance with another aspect of the present
invention.
FIG. 12 is an illustration of the laser perimeter awareness system
embodied on an aircraft search vehicle searching a 360.degree.
perimeter around the search vehicle.
FIG. 13 is an illustration of a search and rescue application of
the laser perimeter awareness system on a marine search vessel in
accordance with another aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Developed initially for helicopters to avoid striking power lines
and other ground obstacles, wide field scanning laser obstacle
awareness systems such as the system disclosed in the U.S. Pat. No.
6,542,227, issued Apr. 1, 2003, for example, have been found
applicable to monitoring objects within a perimeter around a
vulnerable target for threat awareness and to search and rescue
operations which will become more evident from the description
found herein below. The aforementioned U.S. Pat. No. 6,542,227
which is assigned to the same assignee as the instant application
is hereby incorporated by reference herein for providing greater
detail of the structure and operation of an exemplary scanning
laser obstacle awareness system (LOAS). In the development and
testing of the LOAS over water several key phenomena were
discovered. As noted in the aforementioned U.S. patent, the
exemplary LOAS uses a 1550 nm near-infrared wavelength laser with
variable fields of view, a distributed fiber optic architecture,
and an ability to detect very fine objects at long ranges.
Moreover, when scanned over water at oblique incidence angles,
specular reflection and absorption were noted from the water
surface. For example, when the incident laser energy transmitted
from the LOAS strikes the water surface, it is reflected in a
direction other than back to the laser receiver of the LOAS.
However, floating objects in or on the water scatter this laser
energy back into the direction of the laser receiver. As such, only
the floating objects will register a laser object profile return
when the LOAS is employed in this fashion. Thus, dominated by
scattering, any object floating on the surface of the water can
result in a laser return. The level of the laser return is a
function of the object size, laser power, radiated beam divergence,
and laser receiver field of view. Testing has shown the ability to
detect swimmers, waterfowl, and other small watercraft several
hundred meters down range of the LOAS.
With this discovery, the LOAS originally developed to detect power
lines while in flight, may now be applied to scan the water surface
to monitor a perimeter about a target or zone thereof for potential
threats or even aid in the search and rescue of individuals lost at
sea. Unlike conventional passive infrared systems that rely on the
thermal difference between the body and water, using a LOAS in this
fashion and exploiting the scattering and absorption
characteristics thereof over water can increase the detection
performance, as it is independent of thermal gradients which are
needed for the detection of floating bodies with passive infrared
imaging systems as noted above. Using the laser scanning and return
detection technologies to automate the search pattern over water
will generate a geo-located map of no laser echoes (water) and
laser echoes (objects such as a terrorist, downed pilot or
debris).
Using a LOAS in this fashion exploits the very narrow emitted laser
beam diameter, on the order of 2 mrad of divergence, for example.
Since the LOAS has been demonstrated to detect 5 mm wires at
hundreds of meters (see U.S. Pat. No. 6,542,227), it clearly has
the ability to detect fine diameter objects at significant ranges.
Exploiting this same performance over ground or water will result
in similar sensitivity and an ability to detect small ground and/or
waterborne objects.
Another noteworthy point is that a LOAS has none of the
aforementioned limitations of radar detection systems and can be
used to detect the same targets as the radar system with a very
high degree of directivity, without side lobes or multi-path
issues. Yet another very significant benefit of employing a LOAS in
perimeter security applications is the ability to obtain very short
range resolution, on the order of six inches. This currently cannot
be achieved using conventional radar systems. Finally, it is
possible to deploy an array of laser scanning devices or heads in a
LOAS for monitoring a perimeter completely surrounding a target
site with little or no inter-system cross-talk between scanning
devices. More specifically, each laser scanner may be designed to
emit and detect only a narrow band of optical frequencies. It is
possible to place an array of scanners in close proximity by
selecting a unique frequency, or channel, for each scanner.
Cross-talk among the scanners is reduced or eliminated through the
use of standard optical bandpass filters. The optical bandwidth of
these filters can be one part in ten thousand, with an out-of-band
rejection of 10.sup.5, for example. Given this level of filter
performance, it is possible to parse a large number of channels
within the gain profile of many solid-state lasers (e.g. the C-band
of Er:fiber lasers).
Yet another derivative of this technology is the ability to use the
same LOAS embodiment over water or land or combinations thereof. In
either application, the laser echo returns can be compared to
previously measured returns to examine the scene for changes. With
this level of detection performance, the device can be used to
secure military installations over wide areas and present to
security personnel information that relates to threats that have
been identified by movement, such as an intruder crossing a
field.
When a LOAS is installed in a maritime environment, the same device
can scan and monitor the perimeter of a ship, for example, for
small watercraft or swimmers at ranges less than 3 km. This range
is critical as often a ship's radar performs better beyond 1 km due
to near field ground clutter returns. Once ground or waterborne
objects have been detected, it is possible to query other video and
optical systems for confirmation as will become better understood
from the description found herein below. Likewise, this object
information can be fused with other automated fire control systems
to suppress suspected threats.
FIG. 1 is a top view of a laser perimeter awareness system suitable
for embodying the broad principles of the present invention.
Referring to FIG. 1, a plurality of laser scanning devices 10, 12,
14, and 16 may be disposed on a target 20 which may be a marine
vessel, a building, an aircraft, a pier of a port and the like, for
example. Each scanning device 10, 12, 14 and 16 covers azimuthally
a correspondingly respective perimeter zone 22, 24, 26 and 28 with
a scanning laser beam. Each zone is bounded by lines of azimuth.
For example, zone 22 is bounded by azimuth lines 30 and 32; zone 24
is bounded by azimuth lines 34 and 36; zone 26 is bounded by
azimuth lines 38 and 40; and zone 28 is bounded by azimuth lines 42
and 44. Note that the zones may be overlapping in azimuth patterns.
Each zone may also include an azimuth center line, like the
dot-dashed line 46 shown for zone 26.
As shown in FIG. 2 which is a cross-sectional view of one of the
laser perimeter scans of the embodiment of FIG. 1, each scanning
device 10, 12, 14 and 16 may oscillate its laser beam or path 50
back and forth in elevation covering an elevation angle .theta.
which in turn scans the laser beam across a ground or water
perimeter line denoted as 48. Thus, as the laser beam is scanned in
azimuth and oscillated in elevation, it covers its respective
perimeter zone with a sinusoidal pattern which m ay have an azimuth
scan frequency of approximately two hertz (2 Hz), for example.
During each azimuth scan which may take on the order of one-half
second, laser energy is pulsed along the scanning beams or paths at
a predetermined rate which may be approximately 70,000 pulses per
second (pps), for example. Time of flight techniques on the laser
echoes may be employed by the laser system to identify objects and
the corresponding locations thereof within the perimeter zone.
While the perimeter zones or scanned fields of view of the scanning
devices 10, 12, 14 and 16 of the embodiment of FIG. 1 are shown
fixed, it is understood that they may be varied to respond to an
emerging threat. For example, it is well known that ports and piers
in the US are supported by a structural system of submerged
pilings. Waterways between these pilings permit access to swimmers
and kayakers which presents a potential threat of sabotage. Thus,
by varying the scan zone of a scanning device of the embodiment of
FIG. 1 to a narrow corridor in azimuth, areas under a pier may be
monitored in greater detail for intruders. Intruders in these areas
may be detected using the laser back scatterings over water and a
threat alert provided to render a situational awareness.
A laser beam scanning device suitable for use in the embodiments of
FIGS. 1 and 2 is illustrated in FIG. 3 and an exemplary embodiment
of the optical components thereof is depicted in FIG. 4. Referring
to FIG. 3, a scan head 300 controls movement of the oscillating
laser beam scan pattern at least along an azimuth axis 302 and an
elevation axis 304. The extent of the laser beam oscillation in
elevation angle .theta. is shown by the dot-dashed lines 306. A
bottom 308 of the scan head 300 may be mounted to a surface of the
target site, like the top of a building, for example, such as shown
in the sketch of FIG. 2. A window area 310 of the scan head 300
through which the beam scans are emitted would be pointed in the
direction of the corresponding perimeter scan zone. A fiber optic
cable 311 carrying the pulsed laser energy from a laser source,
which will be described in greater detail herein below, may be
passed into the scan head 300 through an opening 312 at the bottom
308 thereof or through an opening in a side area 320 described
below.
Optical elements within the scan head 300, which will be described
in greater detail in connection with FIG. 4 below, cause the beams
passed by the cable 311 to be oscillated in elevation through the
scan angle .theta.. A conventional motor assembly (not shown)
within the scan head 300 controls movement of an upper portion 314
thereof an azimuth scan angle about the axis 302 sufficient to
cover the corresponding perimeter zone. This movement occurs along
a seam 316 between the top and bottom portions, 314 and 308,
respectively, and effectively moves the oscillating laser beams 306
along with the upper portion 314 which projects the beam scan
pattern through a sinusoidal pattern much the same as that
described in connection with the example of FIG. 2.
Another portion 318 of the scan head 300 which includes the window
area 310 and falls within the portion 314 moves azimuthally with
the portion 314. Another conventional motor (not shown) disposed
within the scan head 300 controls movement of the portion 318 about
the axis 304 permitting control of the oscillating laser beams 306
in elevation, for example, which may extend the perimeter zone
outward from or inward to the target site. In the present
embodiment, the window area 310 of the portion 318 may be
controlled to move upward and inside the portion 314 to protect it
from the environment when not in use. The corrugated skin or
surface in the area 320 at the bottom portion 308 acts as a heat
sink to improve the transfer of heat away from the scan head 300
during operation thereof. Alternately, in the case where heat
dissipation may not be needed by the drive systems of the scan head
300, the side area 320 may be smooth.
A sketch exemplifying the optical elements inside the scan head 300
is shown in FIG. 4. Referring to FIG. 4, the fiber optic cabling
311 may be aligned with the axis of the input aperture of a beam
expander 322 to guide the laser beam therethrough. The expanded
beam exiting the expander 322 over optical path 324 may be
reflected from an oscillating mirror 325 over a scan of optical
paths between path 326 and path 328 about a central axis 330. The
oscillated laser beams exit the scan head 300 through the window
310. In the present embodiment, the oscillating mirror 325 may be
driven by a mechanically linked resonant scanner unit 332 at an
oscillation frequency of approximately one hundred hertz, for
example. Reference is made to the U.S. patent application Ser. No.
10/056,199, entitled "Silicon Wafer Based Rotatable Mirror", filed
Jan. 24, 2002, and assigned to the same assignee as the instant
application, which application being incorporated by reference
herein for providing a suitable resonant scanner and oscillating
mirror assembly in greater detail. While the present embodiment
uses a resonant scanner assembly for oscillating the laser beam, it
is understood that other elements may be used for oscillating the
laser beam, like a transparent liquid crystal scanner or microlens
array scanner, for example, without deviating from the broad
principles of the present invention.
Return laser energy may follow the same optical scan paths as their
emitted beams for return to the optical fiber cable 311 as
described herein above. A bipolar laser beam return path may be
embedded in the fiber optic cable 311. The window area 310 may
comprise a clear, flat, zero power optical element made of a
material like glass, for example, so as not to interfere
substantially with the scan pattern of the exiting laser beams. In
the present embodiment, the resonant scanner assembly 325,332 and
window 310 are structurally coupled to move together along the
azimuth path 334 and elevation path 336 to cause the oscillating
laser beams 326-328 to move along therewith. In this manner, the
oscillating laser beams are forced to move in azimuth with the
movement of the scan head 300 to form a sinusoidal scan pattern
shown at 338. Also, in the present embodiment, the various scan
motors for controlling the azimuth, elevation and oscillations of
the laser beams within the scan head may include position sensing
elements which generate analog signaling of the specific position
of the laser beam in the controlled scan of the perimeter scan as
is well known to all those skilled in the pertinent art, the
significance of which being more fully explained hereinbelow.
While the scan head 300 of the present embodiment is described as
utilizing a beam expander 332, it is understood that in some
applications, the beam expander 332 may not be used in which case,
the pulsed laser beam exiting the fiber optic cable 311 may be
guided directly to the oscillating mirror 325 over the path 324.
The natural divergent expansion of the laser beam as it exits the
fiber optic cable 311 may provide a sufficient beam width. In some
cases, a collimating lens may be configured in the path 324 to stop
the beam expansion and collimate the beam prior to oscillation.
Also, as noted above, the present invention may be embodied to
include more than one scan head 300 mounted at different locations
on the target site as shown in FIG. 1. Depending on the
application, some of the scan heads may utilize fewer optical
elements and less scan angle than that described for the embodiment
of FIGS. 1 and 2. It is also understood that the oscillation angle
.theta. of the resonant scanner 332 may be controllably varied to
become narrower or wider for different views.
A block diagram schematic of a laser perimeter awareness system
(LPAS) suitable for use in the embodiment of FIG. 1 is shown in
FIG. 5. Referring to FIG. 5, a common laser source 60 which may be
a Erbium:Glass fiber laser manufactured by IPG Photonics, for
example, may generate laser energy on the order of 15 kilowatts
peak power at a near infrared wavelength range of 1550 nanometers
(nm), for example, and at a pulse repetition rate of approximately
70,000 pps. The laser energy pulses may be conducted from the
common source 60 to the plurality of scanning heads 10, 12, 14 and
16 over a distributed fiber optic path architecture 62 through
conventional optical couplers, for example. The scanning heads 10,
12, 14 and 16 scan the laser energy in laser beams or paths over
respective perimeter zones as described in connection with the
embodiment of FIGS. 1-4. Laser energy echoes received by each laser
head from its respective perimeter zone may be optically conducted
over a separate or bipolar fiber optic path to a light detector.
For example, laser echoes from head 10 may be conducted over a
fiber optic path 64 to a light detector 66 and laser echoes from
head 16 may be conducted over a fiber optic path 68 to a light
detector 70. The other heads 12 and 14 will have a similar
arrangement. The light detectors convert the received light echoes
into electrical analog signals representative thereof.
If inter-system cross-talk between the plurality of scanning
devices is considered an issue, then the common laser source 60 may
emit a narrow band of optical frequencies for each scanner and
unique thereto. Thus, it is possible to place an array of scanners
10, 12, 14 and 16 in close proximity by selecting a unique laser
frequency band, or channel, for each scanner. Cross-talk among the
plurality of scanners may be reduced or eliminated through the use
of standard optical bandpass filters internal to the optics of the
scanner. That is, an optical bandpass filter may be disposed in
each scanner and designed to pass only the narrow band of optical
frequencies unique thereto for scanning and backscatter reception.
The optical bandwidth of these filters may be one part in ten
thousand, with an out-of-band rejection of 105, for example. In an
alternate embodiment, an individual laser source may be assigned to
each scanner for emitting the narrow band of optical frequencies
unique thereto. Each individual laser source may be embodied either
internal or external to the scanner. Given the foregoing described
level of optical filter performance, it is possible to parse a
large number of channels within the gain profile of many individual
scanner solid-state lasers (e.g. the C-band of Er:fiber
lasers).
In an alternate embodiment, an optical switch may be disposed in
the output optical path of the common laser source 60. The optical
switch may be controlled to time multiplex the output laser beam of
source 60 to a plurality of fiber optic paths leading to the
corresponding plurality of scan heads 10, 12, 14 and 16. Within
each corresponding fiber optic path may be return optic fibers for
receiving the return laser beam energy from the respective scan
head and guiding it over a different optical path than the directed
source laser beam. A suitable high-speed optical switch for this
purpose may be a flip mirrored element mounted with vertical hinges
to be controlled in a horizontal rotation thereabout and mounted
with horizontal hinges to be controlled in a vertical rotation
thereabout. The optical switch may be fabricated on a substrate
using microelectromechanical system (MEMS) techniques with
miniature motors coupled to the hinged mountings for controlling
the movement of the mirrored element to direct the output laser
beam to one of the scan heads 10, 12, 14 and 16 at any given
time.
In this manner, the output laser beam from source 60 may be time
multiplexed among the aforementioned scan heads by controlling the
optical switch with a control signal which positions the motors of
the switch. Laser energy echoes may then be returned from the
corresponding scan head over a separate or bipolar return path. It
is understood that the flip mirror element is merely an exemplary
embodiment of the optical switch and that other embodiments may be
used just as well. For example, a rotating disc having a portion
that is substantially clear to direct passage of the output laser
beam along to one of the scan heads, and a portion that has a
reflective coating to cause the beam to be reflected to another
scan head, such paths may be positioned by a motor controlled to
direct the output laser beam to a designated scan head by passage
or reflection thereof.
Also, in the embodiment of FIG. 5, each scanner 10, 12, 14 and 16
generates azimuth (AZ) and elevation (EL) signals representative of
the position of the laser beam in its perimeter zone scan. For
example, scanner 10 generates AZ and EL signals over signal lines
72 and 74, respectively, and scanner 16 generates AZ and EL signals
over signal lines 76 and 78, respectively. Each light detector
conducts the electrical echo signals thereof to digital inputs of a
programmed digital signal processor 80. For example, the echo
signals from detectors 66 and 70 are provided to designated digital
inputs of the processor 80 over signal lines 82 and 84,
respectively. In addition, the analog signals representative of AZ
and EL from each of the scanners may be digitized by an
analog-to-digital (A/D) converter and the digitized AZ and EL
signals provided to the processor 80. This may be performed
autonomously by the A/D or under program control of the processor
80. In the present embodiment, each scanner may have its own
individual A/D. For example, the AZ and EL signals from scanners 10
and 16 are digitized by A/D converters 86 and 90 and the resulting
digital AZ and EL words are provided to the processor 80 over data
lines 88 and 92, respectively. The other scanners of the plurality
will have a similar arrangement. It is understood that a common A/D
converter may be time multiplexed for digitizing all of the AZ and
EL signals from the plurality of scanners just as well. Moreover,
if echo signal intensity is desired to a greater resolution than
one-bit, as in the present embodiment, for the processing of echo
signals, then the outputs of the light detectors may be digitized
by an A/D converter in a similar manner as described for the AZ and
EL signals, for example. None of the aforementioned modifications
will deviate from the broad principles of the present
invention.
As will become more evident from the description below, each time
the processor 80 receives an echo signal from a scanner, it stores
the corresponding AZ and EL positions thereof in the scan to form a
scene image of the scan in a designated portion of a memory 94
coupled thereto over control, address and data lines 96, for
example. The range of each echo is determined by the processor 80
in the present embodiment using well-known time of flight
techniques. Thus, the echo signals from the scanners are correlated
and used to form scene images for each perimeter zone scan or
portion thereof of each scanner. The echoes making up each scone
image may be considered picture elements or pixels for image
processing as will become more evident from the following
description.
In the present embodiment, the processor 80 also controls the
positioning of a spotlight using a position control loop 98 to
visually track a high priority threat identified in one of the
perimeter zones, and the positioning of a forward looking infrared
(FLIR) camera or video camera using another position control loop
100 for displaying a thermal or video scene surrounding the threat
on a display to decision making personnel. More specifically, a
digital signal representative of a desired spotlight position may
be output from the processor 80 over signal lines 102 to a + input
of a summer 104 which provides an error signal 106 to a spotlight
position controller 108. In response to the error signal 106, the
controller 108 drives a spotlight assembly 110 with signal 109 to a
position to direct its light towards the identified threat. An
actual light position of the spotlight 110 is sensed and provided
as feedback to a - input of the summer 104 over signal line 112.
The controller 108 will drive the spotlight to its desired position
designated by signal 102 until the error signal 104 approaches
substantially zero and thereafter, vary the spotlight position in
response to a varying desired position in order to visually track
the identified threat.
Likewise, a digital signal representative of a desired camera
position may be output from the processor 80 over signal lines 114
to a + input of a summer 116 which provides an error signal 118 to
a camera position controller 120. In response to the error signal
118, the controller 120 drives a camera assembly 122, either FLIR
or video or both, with signal 124 to a position to view the
identified threat within the field of view thereof. An actual
camera position of the assembly 122 is sensed and provided as
feedback to a input of the summer 116 over signal line 126. The
controller 120 will drive the camera of assembly 122 to its desired
position designated by signal 114 until the error signal 118
approaches substantially zero and thereafter, vary the camera
position in response to a varying desired position in order to
maintain the identified threat in the field of view thereof. A
video image of the camera's scene is provided over signal line 130
to a display 132 via an image/text overlay circuit 134. In
addition, data representative of the position and the significance
of an identified threat maybe provided by the processor 80 to a
display controller 138 over digital signal lines 136, for
example.
The significance data of the threat may comprise parameters of
shape, size and priority as will become more evident from the
following description. From the threat significance parameter data,
the display controller 138 may generate video signals
representative of an image of and corresponding text characterizing
the threat together with a position thereof in the video image. The
generated threat video signals may be provided to the overlay
circuit 134 over signal lines 140. In the overlay circuit 140, the
generated threat video signals may be displayed separately in a
"map" like image on the display monitor 132 or superimposed over
the video signaling from the camera 122 for display on the display
monitor 132. Accordingly, responsible personnel may view the
threat(s) from the video images of the display monitor 132 and/or
from a visual inspection of the spotlighted area and make a
decision on whether or not to take defensive counter-measures.
While the position control loops 98 and 100 have been described in
the embodiment of FIG. 5 as being outside of the processor 80, it
is understood that the functions described for the control loops 98
and 100 may just as well be programmed into the processor 80 in an
alternate embodiment. In such an alternate embodiment, the
processor 80 would generate drive signals 109 and 124 directly,
perhaps through corresponding digital-to-analog (D/A) converters,
and receive corresponding feedback signals 112 and 126 directly,
perhaps through analog-to-digital (A/D) circuits. Also, if the
position control loops 98 and 100 are of the analog variety, a D/A
converter may be included in each summer 104 and 116 to convert the
digital position signals to analog, for example. The use of D/A and
A/D circuits for these purposes is well known to those persons of
ordinary skill in the pertinent art.
FIGS. 6A and 6B depict an exemplary program flowchart suitable for
use in programming the processor 80 of the embodiment of FIG. 5 for
performing functions of the laser perimeter awareness system in
accordance with the broad principles of the present invention.
Referring to FIGS. 6A and 6B, the program flow of blocks 152, 154
and 156 are sequentially executed in the background to follow in
time the perimeter zone scans of the plurality of scanners, to
gather the echo data from the received echo signals thereof which
data comprising such parameters as amplitude, time of arrival
(TOA), elevation (EL) and azimuth (AZ), for example, and to form an
image scene for each complete scan. The scans of the plurality of
scanners may be performed simultaneously, preferably, but not
necessarily, synchronized to each other, or sequentially around the
perimeter in either a clockwise or counter-clockwise direction. In
either case, once a complete scan image is formed as determined by
block 156, an image complete flag is set and the gathered data
representative of the scan image is correlated to its corresponding
perimeter zone and stored in a designated portion of memory 94, for
example. Note that there will be as many scan image scenes as there
are scanners and corresponding perimeter zones. Once the scene
image data is stored in memory, the program resets the image
complete flag in block 158 and continues executing blocks 152, 154
and 156 in the background to form the next scene image.
As each image scene is completed, decisional block 160 determines
if a reference image scene has been stored for the corresponding
perimeter zone. If not, the current image scene may be classified
as the reference scene image for the corresponding zone in block
162; else, the current image scene is stored and compared with the
pre-classified reference image scene of the same zone in block 164
to identify moving objects. A reference image scene may be a
composite of more than one image scene. The comparison of image
scenes may be performed through well-known pixel analysis
algorithms comparing the position of the pixels of an object in the
current scene to the position of the pixels of the same object in
the reference scene. Thus, a change in position of the same object
from one scene image to another is indicative of movement thereof.
In decisional block 166, it is determined if there are any moving
objects identified in an image scene. If not, processing is
diverted to block 162 in which the current image scene data may be
classified as or combined with the old reference image to form a
new reference image for the corresponding zone. The program then
waits until data is gathered for the next complete image scene as
determined by block 156.
If block 166 determines there are moving objects in the zone from
the current image scene, a moving object from those identified is
selected and the range, bearing and elevation thereof is determined
in block 168. Next in block 170, it is determined if the selected
object has been previously identified. If not, the object is
classified or tagged in block 172 and a track flag is set for the
tagged object in block 174. Since the object was not previously
identified, it has no prior historical data from which to asses the
threat thereof which will come from subsequent image scenes from
the corresponding zone. Consequently, the threat analysis
processing may be by-passed and processing may continue at block
176 in which it is determined if there are any more moving objects
identified from the current image scene.
If the selected object was previously identified as determined by
block 170, then it is next determined in block 178 if the track
flag was set for that object. If not, then the track flag is set in
block 174. If the track flag was set, then this is an indication
that the program is tracking the movement of the object and has
historical data from which to determine a threat priority which is
performed in block 180. In the present embodiment, the threat
priority may be calculated based on a well-known constant bearing,
decreasing range (CBDR) algorithm. The illustration of FIG. 7 is a
composite of stored historical data of two tagged moving objects,
represented by small circles, over a plurality of scene images. The
target site is denoted by an X in FIG. 7. Each object O in FIG. 7
is referenced by two subscripted numbers XY, where the X subscript
identifies the tagged object and the Y identifies the scene image
from which the position thereof was determined. For example,
O.sub.11 represents object 1 taken from scene image 1, O.sub.12
represents object 1 taken from scene image 2 and so on. Likewise,
O.sub.21 represents object 2 taken from scene image 1 and so
on.
Both objects 1 and 2 are positioned with respect to the target site
in the illustration based on their range and bearing from a
centerline (C/L) of the scan zone (see FIG. 1) for each scene
image. For example, object O.sub.11 is positioned at a range
R.sub.11 and a bearing angle -.theta..sub.i, object O.sub.12 is
positioned at a range R.sub.12 at the same bearing angle
-.theta..sub.1 and so on. Similarly, object O.sub.21 is positioned
at a range R.sub.21 and a bearing angle .theta..sub.21, object
O.sub.22 is positioned at a range R.sub.22 and a bearing angle
.theta..sub.22 and so on. The dashed lines connecting the commonly
tagged objects 1 and 2 represent a track of the corresponding
moving object. Accordingly, since object 1 is being tracked on a
substantially constant bearing with a decreasing range with respect
to the target site among scene images, it will have a higher threat
priority than object 2 which is being tracked as substantially
traversing or moving away from the target.
After the threat priority for the moving object is set in block
182, it is queued into a table stored in a designated portion of
memory 94 by block 184. An example of such a queue table is shown
in FIG. 8. Note that objects are listed in the table from the
highest to the lowest threat priority. For example, in the table of
FIG. 8, object 1 has the highest threat priority denoted as 7,
object 3 has the next highest denoted as 5 and so on down the list.
In the present embodiment, a threat priority of 10 may be
representative of the highest and 0 the lowest, for example. The
queue table listing may be updated in real time as the program is
being executed. For example, if object 1 starts deviating in
bearing away from the target X in subsequent scene images, the
threat priority thereof will decrease and, consequently, its row
listing in the queue table will fall. Next, in block 186, data on
the moving object of the queue table listing may be output from the
processor 80 over data lines 136, for example, to the display
controller 138 to effect its display on the screen of the display
monitor 132. The object may be displayed in the form of a symbol or
icon with corresponding text characterizing its threat priority
level.
Thereafter, in block 188, the shape of the moving object is
determined using pixel analysis on the pixels of the current scene
image, preferably through contrasting edges and lines as is
well-known in the pertinent art. Next, in block 190, the object
shape is compared using well-known pixel pattern recognition
techniques, for example, with pre-stored shapes or signatures of
known objects which may be considered friendly objects, such as
certain types of marine vessels, birds, and the like, for example.
The comparison may result in a match number or match percentage
which may be used as the criterion for determining whether or not
the object is friendly in decisional block 192. If determined not
friendly, then in decisional block 194, it is determined if the
threat priority level of the object is above a predetermined X
level, like 7, for example. If so, position signals are output over
signal lines 102 and 114 to position the spotlight 110 to
illuminate the threat and camera 122 to view the threat,
respectively, for visual tracking as described herein above. These
position signals will continue to control the spotlight and cameras
to track the threat until the priority threat level thereof falls
below the predetermined X level. In this manner, the threat may be
visually inspected and confirmed by responsible personnel, who may
be alerted to the threat via the display 132, for example, for
making decisions on possible defensive counter-measures. The
responsible personnel may also determine from a visual inspection
that the threat is not offensive or even friendly and avoid false
alerts. All in all the system provides a sound situational
awareness of the perimeter surrounding the target site.
Of course, if the object is determined to be friendly by block 192,
then blocks 194 and 196 may be by-passed. In any event, program
execution continues at block 176 in which it is determined if there
are any more moving objects in the current scene image. If there is
another moving object in the current scene, program execution
continues at block 168 and the steps 168-196 are repeated for the
next object and so on until all of the moving objects of the
current scene are processed. When there are no more moving objects
in the current scene image to be processed, then the program
execution waits until the next scene image is completed as
determined by block 156 and the processing is repeated for the next
scene image as described herein above.
Accordingly, the LPAS identifies, tracks and profiles objects
entering the various controlled zones of the perimeter of the
target from meters to hundreds of meters away. In accordance with
another aspect of the present invention, an automated
authentication system may be included in or with the LPAS to permit
a potential threat, once detected by the LPAS, to authenticate
itself using such signaling as a coded assess radio frequency (RF)
or infrared (IR) signal, entry card, or two-way pager, for example.
On board the target, which may be an aircraft, ship, vehicle,
building or the like, for example, a known list of authenticated
access codes may be pre-stored for use in approving entry of and
communicating back to the identified object. Denied entry may
result in the generation of an alarm with subsequent rules of
threat classification and engagement. This authentication system
would be particularly useful in securing high value assets such as
Air Force One, carriers, and special military aircraft operating in
high ground or water threat environments. The system may be also
applied to the commercial aviation industry.
In the commercial aircraft industry, for example, an aircraft may
be equipped with a plurality of laser scanning laser heads as
described in connection with the embodiment of FIG. 1, for example.
Thus, four controlled zones may be established around the aircraft
to monitor and track baggage handlers, fuel providers, food
deliverers, and others. Once these individuals enter the controlled
zones, they would be identified by the LPAS and required to
communicate an access code to the automated authentication system
disposed on-board the aircraft. This may be performed by the
identified individual with an automated RF tag id from a personal
transmitter. The automated authentication system on the aircraft
may then enter into an encrypted exchange with the identified
individual. Access authentication could be achieved with personnel
two-way paging, for example, to reduce system cost. If the exchange
was unsuccessful or if suspicious behavior is detected by the
aircraft's LPAS, notification may be sent to airport security. The
authentication system may have the capacity to store each entry,
time, position, and other pattern information. This data set may be
then communicated to the airport security office prior to departure
of the aircraft for security approval. The data set may be stored
on the aircraft and at the airport terminal and could remain active
for a predetermined time period, like 48 hours, for example.
FIG. 9 is an illustration of an automated authentication system
suitable for embodying this aspect of the present invention. In the
embodiment of FIG. 9, the target 20 may be an aircraft, for
example, showing one of the plurality of laser scanning heads of
the LPAS. The scanning head 10, 12, 14 or 16 scans its laser beam
50 over a zone of the perimeter of the aircraft as described herein
above. Within the zone, it may detect an object 200 which may be a
an authorized service provider or an intruder. The LPAS passes the
position data of the detected object to an authentication system
202 for authentication of the object 200.
FIG. 10 is a block diagram schematic of an exemplary embodiment of
an authentication system suitable for use in the embodiment of FIG.
9. Referring to FIG. 10, an authenticator unit 204 is coupled to an
LPAS 206 over a communication link 208 which may be hard wires,
optical fibers, wireless RF, wireless infrared, and the like, for
example. The authenticator unit 204 may be coupled to a memory 210
over data lines 212, to an encrypter unit 214 over data lines 216,
and to a position control unit 218 of an antenna 220 over data
lines 222. The memory 210 may be used to pre-store authentication
codes of various service providers. In turn, the encrypter unit 214
is coupled aver signal lines 226 to a transmitter/receiver unit 224
for the antenna 220. An exemplary operation of the embodiment of
FIGS. 9 and 10 is as follows.
As the LPAS identifies the object 200 in a perimeter zone, it may
pass data on the object 200 to the authenticator unit 204 over the
communication link 208, such data including the location of the
object 200. In response, the authenticator unit 204 may send
position signaling over lines 222 to the position controller 218 to
position the antenna 220 in the direction of the object 200.
Concurrently, the authenticator unit 204 may send a coded
interrogation signal over lines 216 to the encrypter unit 214 which
encrypts the interrogation signal and passes it to the transmitter
portion of unit 224 over signal lines 226 for transmission through
antenna 220 to the object 200. The wavy line 230 represents the
interrogation transmission from the antenna 220 of the system
202.
If the object 200 is an authorized service provider, it will
receive and respond to the interrogation transmission 230 with its
personal communicator which may be a hand-held two-way pager with
the capability of transmitting a unique encrypted authorization
code, for example. The wavy line 232 in FIG. 9 represents an
encrypted authorization code transmission from the personal
communicator of the object 200. The encrypted transmission 232 is
received by the receiver portion of unit 224 via antenna 220 and
passed over lines 226 to the encrypter unit 214 wherein it is
decrypted and passed to the authenticator unit 204 over lines 216.
When the authenticator unit 204 receives the authorization code, it
may compare it to the pre-stored authorization codes of the memory
210 to establish whether or not it is a proper authorization code.
If an authorization code is not received from the object within a
preset period of time or if the authorization code is not proper,
then the authenticator unit may alert airport security, preferably
by an encrypted signal transmitted over the antenna 220.
Moreover, if the received authorization code is determined to be
proper, then the authenticator unit 204 may be operative to
establish whether the service provider associated with the
authorization code should be at the location at the given time. The
authenticator unit 204 may request such information of the airport
security, for example, via encrypted signals transmitted from
antenna 220 which may include the unique authorization code of the
service provider in question, for example. This information may be
conveyed from the airport security to the automated system 202 via
antenna 220 in response to its request and passed to the
authenticator unit 204 via the receiver portion of unit 224 and the
encrypter 214. The authenticator unit 204 may then compare the
information received from airport security with what it has
determined to authenticate access of the service provider to the
aircraft. If the authenticator 204 detects a discrepancy in the
whereabouts of the service provider, it will alert airport security
via an encrypted transmission. In this manner, the perimeter about
a target may be monitored for intrusion by unauthorized
personnel.
In summary, the LPAS of the present invention has many possible
applications. For water security, the LPAS uses scanning laser
beams and pulsed time of flight methodology to cover a given
perimeter surrounding a marine vessel. Each laser beam is scanned
azimuthally in a sinusoidal pattern across the corresponding
perimeter zone using a resonant scanner which oscillates in a back
and forth fashion at approximately 2 Hz, for example. Laser energy
is primarily reflected from the water surface away from the scanner
and is partially absorbed by the water. Water surface breaching
objects scatter laser energy into the direction of the receiving
optics of the scanner. As such, the water can become invisible to
the laser energy due to scattering thereby making floating objects
highly visible. This implicit clutter reduction scheme exploits the
physical phenomena of specular reflection of laser light on water.
By exploiting the reflection of the laser energy on the surface of
water, floating objects can be easily detected by the various
scanners of the LPAS.
Likewise, using the variable scan field of view of a scanner of the
LPAS, it is possible to scan very narrow corridors to monitor the
waterway under a pier for intruders, for example. Accordingly, the
LPAS can scan these narrow corridors to detect these threats and
provide an awareness thereof. Another side benefit of the surface
scattering mechanism of the various laser scanners of the LPAS is
the ability to aid in antisubmarine warfare by sensing and tracking
wake of periscope. Cavitation from the periscope and water craft
propellers often result in small bubbles. The assembly of these
bubbles, white foam, results in back scattering of laser light
(echoes) towards the laser receiver. These echoes remains as long
as the bubbles are present, often lasting for several minutes.
Similarly, this can also be visualized from watercraft to detect
the prior track.
Another application may be in search and rescue where individuals
lost at sea may be detected using the LPAS to scan the laser beam
over the water surface at oblique incidence angles with a very
narrow emitted laser beam diameter, on the order of 2 mrad of
divergence, for example. When the incident laser energy transmitted
from the LPAS strikes the water surface, it is reflected in a
direction other than back to the laser receiver of the LPAS.
However, floating objects in or on the water scatter this laser
energy back into the direction of the laser receiver. Thus,
dominated by scattering, any object floating on the surface of the
water can result in a laser return. As such, only the floating
objects will register a laser object profile return in an image
scene which may be conveniently detected when the LPAS is employed
in this fashion. The level of the laser return is a function of the
object size, laser power, radiated beam divergence, and laser
receiver field of view.
Accordingly, the LPAS may be applied to scan the water surface to
monitor a perimeter about a search vehicle or zone thereof for
aiding in the search and rescue of individuals lost at sea. Unlike
conventional passive infrared systems that rely on the thermal
difference between the body and water, using a LPAS in this fashion
and exploiting the scattering and absorption characteristics
thereof over water can increase the detection performance, as it is
independent of thermal gradients which are needed for the detection
of floating bodies with passive infrared imaging systems as noted
above. Using the laser scanning and return detection embodiments
described herein above, the search may be automated by using the
search pattern over water to generate a geo-located map or image
scene of no laser echoes (water) and laser echoes to detect
floating objects, such as a lost individual, downed pilot or
debris, for example.
FIG. 11 is an illustration of an aircraft search vehicle 350, like
a helicopter, for example, having the LPAS disposed on-board with
at least one of the scanning heads 10 for monitoring a perimeter
zone 352 of the water for an object, like an individual 354 lost at
sea, for example. The scanning head 10 may be similar to the
scanning head 300 described in connection with the FIGS. 3 and 4.
However, some scan head applications may not utilize the azimuth
scan, but rather rely on the movement of the aircraft or other
search vehicle for developing the sinusoidal scan pattern over a
perimeter zone of water. When disposed on the helicopter 350, the
path of the emitted laser beam from the scan head 10 may be tilted
at an oblique incidence angle, like a 45 degree angle, for example,
to the water surface 356. Only floating objects, like the lost
individual 354, will return the laser energy in the direction of
the scanning head 10 for post processing by the LPAS to develop an
image scene as described herein above. In some applications, the
search vehicle 350 may include a plurality of scan heads 10, 12, 14
and 16 to scan a 360.degree. perimeter 358 of water under and
surrounding the vehicle 350 searching for the lost individual such
as shown in the illustration of FIG. 12.
This search and rescue application can occur from marine search
vessels as well. As shown in the illustration of FIG. 13, a marine
vessel 360 having the LPAS disposed on-board with at least one of
the scanning heads 10 for monitoring a perimeter zone 362 in the
water for an individual 364 lost at sea. The scanning head 10 may
be similar to the scanning head 300 described in connection with
the FIGS. 3 and 4. When disposed on the marine vessel 360, the path
of the emitted laser beam from scan head 10 may be tilted at an
oblique incidence angle, like a 45 degree angle, for example, to
the water surface 356. Only floating objects, like the lost
individual 364, will return the laser energy in the direction of
the scanning head 10 for post processing by the LPAS to develop the
image scene from which the object may be detected. In some
applications, the marine search vessel 360 may also include a
plurality of scan heads 10, 12, 14 and 16 to scan a perimeter of
water surrounding the vessel searching for the lost individual in a
similar manner as described in connection with the illustration of
FIG. 12. In either embodiment, the control panel of the LPAS may
include a search and rescue (SAR) button to automate the
functionality of the laser scan.
A still further application is in maritime surveillance. It is
known that in some cases, maritime vessels present the ship's name
and home port on the side of the vessel using reflective paint. In
other cases, the company name is painted on the side. Typical
commercial maritime vessels also use a black or IR absorbing paint
on the hull to aid in the visibility of the ship lettering over
long distances. This combination of highly reflective and absorbing
paints, when used in conjunction with a scanning laser beam, allows
one to read the lettering on the ship. Likewise, the side profile
of the size and shape of the ship can be used to further classify
the vessel as noted herein above. This information can be used to
feed other ground systems and as a method of confirming maritime
traffic in an unattended manner.
A still further application is in the field of ground perimeter
security. By laser scanning a perimeter surrounding a ground target
with the LPAS, a 3-dimensional image scene can be assembled in
azimuth, elevation, and range from the received laser energy back
scatterings as described herein above. Scanning multiple times, on
the order of every 5-10 seconds, for example, a clutter map can be
created whereby the data is accumulated and assembled from multiple
passes. The accumulation of data may be then stored in a reference
image, also know as a background clutter map. Switching to
real-time data, each image scene dataset of azimuth, elevation, and
range is compared to the reference clutter map. If the real-time
data matches the clutter map to within a variable distance of
spatial resolution, no processed data is reported. Likewise, if no
representative data point is present in the clutter map, a
difference is noted and displayed on a geo-located map or aerial
photograph. If the target is moving and the data is accumulated and
displayed over a period of time, a track can be displayed of a
moving ground object.
Using a LPAS in this fashion has a distinct advantage as it enables
fine detail detection, high range resolution, and motion detection
in confined spaces where conventional radar is overwhelmed with
ground clutter and can be hazardous to ground personnel. In
addition, this detection technique has the ability to look beyond
fence lines covertly to see ground motion in non-secure areas.
A still further application of the LPAS is in short range airport
traffic control wherein the LPAS may be used in a fashion similar
to ground traffic control radar but over shorter distances, with
finer detection, and with a laser as the illumination source. Using
the scanning laser beam, the area around the flight deck, for
example, can be scanned in real-time. Using the moving ground
target capability mentioned above, it is possible to detect and
track individuals, small vehicles, and other objects such as
wildlife that may be hazardous to aircraft operation or represent a
potential terrorist attempt. The LPAS may be also installed on an
aircraft using a distributed scanning head, fiber optic arrangement
or installed on the ground to monitor around the aircraft. In each
case the geo-located position is know and from returned laser
energy, ground motion can be determined in azimuth, elevation, and
range referenced to the area of interest. As such, secure zones can
be established and monitored. Whenever ground motion is detected,
an alarm is issued and acted upon by security personnel. When
embodied in a security system, the times and locations of
intrusions are established.
In addition, secure access can be automated with the automated
authentication system using coded RF transmitters. When a moving
object penetrates the secure zone, a transmitter on a personal
communicator of the authorized user may issue an encoded key for
access either automatically or in response to a coded interrogation
from the system. The encoded key or authorization code transmission
is received and compared to authorized access ID, time, spatial
position, and motion. When access is authenticated, the alarm
trigger may be de-activated. Conversely when no authentication can
be made, an alarm can be issued and airport security alerted. The
alarm can be issued as a conventional audible alert or used by
other visible cameras or sensors to further interrogate the
intrusion. By tracking the motion, logging the identification, and
comparing to the authorized access, a security log can be recorded
and analyzed. These actions would be undertaken in close proximity
to an aircraft or taxi way, within 1 km of range and a nominal
operating range of 100 m. Likewise, over longer ranges of airport
land, intrusion is also of concern. By using the scanning laser
methodology of the LPAS, it is possible to detect and track moving
ground vehicles and smaller objects not detected by conventional
airport ground traffic radar.
While the present invention has been described above in connection
with a number of embodiments, it is understood these embodiments
were presented merely by way of example and that in no way, shape,
or form is any of the embodiments intended to limit the present
invention. Rather, the present invention should be construed in
breadth and broad scope in accordance with the recitation of the
claims appended hereto.
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